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The following I copied from an earlier post and this the control logic that am using to understand why GPR is not working. Basically, my GPR works if I ground the proper terminal. So, there is continuity on the pink/orange ground wire back to pin 101 of pcm connector. So, if the quote below is true stating that that "if temperate is below 131 F" the GPR activates briefly and I am guessing if the temp is above 131 it wont? Also if there is a sensor malfunction (EOT, BARO) it will not activate. I don't know what temp is being talked about, but with an overnight cold soak this am after overnight dipping into 60's, I had EOT 72F, IAT 58, ECT 180. I have read there may not be an actual ECT but just HOT-COLD. So other than buying a PCM could the failure to ground be some temperature issue? Clearly the ECT is way off the actual?
"The glow plug system is electronically controlled by the powertrain control module. If the temperature is below 55°C (131°F) the powertrain control module will energize the glow plugs immediately after the key is placed in the ON position. Then, depending on the readings from the engine oil temperature (EOT) sensor and the barometric pressure (BARO) sensor, the powertrain control module determines how long the glow plugs will be on.
If either the EOT sensor or BARO (internal to the PCM) malfunction, the GPR will not activate.
The powertrain control module protects the glow plugs by energizing them for short durations if the battery voltage is abnormally high. The purple - (blue) wire is the battery voltage monitoring sensor wire from the GPR to the PCM and is protected by a fusible link."
If you are able to pull the sensor readings, are you also able to see what the PCM is telling the GPR to do? If I'm not mistaking the GPR will always have 12 volts, and the PCM controls the GPR by grounding it. So it is possible there is a bad connection between the GPR and PCM. But if you find the PCM is not activating the GPR, then it's a sensor. I agree with you on the ECT sensor, what sensor is that? Engine coolant temp?
The pink/orange wire connecting to the GPR has continuity back to the PCM connector. The PCM is not giving the ground signal.The ECT (engine coolant temp) was reading 180 on the forscan but engine was cold. should have been maybe 75. I unplugged the sensor and still read 180? Maybe the PCM has defaulted to 180 maybe due to a wiring or other issue? still, I don't know if the ECT even has an effect on the PCM control of the GPR.
The manual I have is for 03, so I can't say in your case. I was going to look it up any ways, but I don't have it handy. If you have a multi-meter you can check resistance through the sensor to atleast tell if it is open or not. I would replace the sensor before springing for a PCM.
So I found out that for 99.5-03 7.3's, the ECT is not monitored on automatic transmissions. I do not know about OBS models. I also looked up the GPR in my 03 7.3 PCM/ECM manual, and the EOT and BARO are used to determine the need for glow plugs. But again, I can't speak to what the case is for your truck. It is starting to look like a PCM problem, but I have never heard of a failed PCM that only stopped controlling the glow plugs. You never specified the year of the truck in question, but judging by the forum you posted in I'm assuming it isn't the truck in your signature!
I'm not a fan of throwing parts at a problem(especially expensive/hard to find parts) and I don't have the manual to help dig deeper into diagnosing your problem. If you could pick up a PCM for $20 at Advance then it would be no big deal, but that isn't the case here. I wish I had more relevant information to bring to the table.
I don't know if this will help much, but here is my 1995 truck using FORScan Lite on a tablet.
Key On ,Engine Off. EOT is 75, PCM is grounding for the glow plug relay to be on.
KOEO, after about 2 minutes, glow plug relay is now off.
Unplugged the EOT sensor, KOEO PCM is grounding for the glow plug relay to be on.
As far as I know the PCM does not read the engine coolant temperature for this vehicle. Was the sensor you unhooked for the coolant temp 1 wire or 2 wire?
I have a similar issue with my truck. I recently replaced my GPR becuaase I was gettting some white smoke a startup like a cold start. After a new Western Plow snow GPR I still get white smoke on some start ups. The truck right now is my DD and it happens probably 10% of the time. I put new GP's in in late 2014
I weas doing some research and the BARO sensor is under the Dash I was going to try that my self.
Does anyone know if they have bad injectgor orings if draining the water seperator would be blackish? I have efuel and was under the truck and dranined it the other day and it looked perfect no oil contamination. I havent puilled the filters tho
Does anyone know if they have bad injectgor orings if draining the water seperator would be blackish? I have efuel and was under the truck and dranined it the other day and it looked perfect no oil contamination. I havent puilled the filters tho
The pressure in the oil rail is at least 5 times higher than the pressure in the fuel rail. So if your injector o-rings are bad the oil pressure will push past those o-rings in into the fuel rail and back to the fuel bowl.
The pressure in the oil rail is at least 5 times higher than the pressure in the fuel rail. So if your injector o-rings are bad the oil pressure will push past those o-rings in into the fuel rail and back to the fuel bowl.
I know, but would I see a darker tinge when draining the water seperator I believe I would.
I'm also not losing oil, I think maybe an injector might not be firing at start up all the time
I've only recently started learning about the differences between the OBS systems vs 99+ so bare with me. What oil leaks into the fuel will go into the return. Some I want to say may linger in the fuel bowl, while most will go back to the tank via the pressure regulator. What goes back to the tank will be diluted before it goes back to the fuel bowl making the evidence less noticeable. The other factor is how bad your injector o-rings are. If they aren't leaking much or it is only on one or two injectors then the amount of oil you are losing will be negligible as well as the signs of leaking O-rings. Even when they are leaking pretty bad it can take a while before you can tell via the dipstick that you are losing oil.
I've only recently started learning about the differences between the OBS systems vs 99+ so bare with me. What oil leaks into the fuel will go into the return. Some I want to say may linger in the fuel bowl, while most will go back to the tank via the pressure regulator. What goes back to the tank will be diluted before it goes back to the fuel bowl making the evidence less noticeable. The other factor is how bad your injector o-rings are. If they aren't leaking much or it is only on one or two injectors then the amount of oil you are losing will be negligible as well as the signs of leaking O-rings. Even when they are leaking pretty bad it can take a while before you can tell via the dipstick that you are losing oil.
Cool good info thanks for the quick reply, any idea why I'm occasionally getting white smoke on a start up?
I don't know if this will help much, but here is my 1995 truck using FORScan Lite on a tablet.
Key On ,Engine Off. EOT is 75, PCM is grounding for the glow plug relay to be on.
KOEO, after about 2 minutes, glow plug relay is now off.
Unplugged the EOT sensor, KOEO PCM is grounding for the glow plug relay to be on.
As far as I know the PCM does not read the engine coolant temperature for this vehicle. Was the sensor you unhooked for the coolant temp 1 wire or 2 wire?
Hope this helps some.
Kevin
Thanks, that pretty much confirms the EOT is the sensor for GPR. The sensor I unhooked was two wire, right by the thermostat flange, what is the one wire on top of the engine front, since it is a van its hard to tell is it is in the intake or water passage. Since my ECT appears jacked up (reading 180 on cold engine) I am hoping to make it the problem with GPR. Don't want to buy a pcm. I am going to sell it soon and a dash switch would be my fix but some people might be scared off.
Cool good info thanks for the quick reply, any idea why I'm occasionally getting white smoke on a start up?
white smoke could be from the glow plugs. If the idle is rough it could also be an injector that doesn't want to work until it gets a little warmed up. If you're looking at the smoke from your mirrors it can be difficult to distinguish white smoke from blue smoke.
Originally Posted by knotreel
I am going to sell it soon and a dash switch would be my fix but some people might be scared off.
If i were a buyer, it would depend on your asking price and what I plan on using the van for.
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